Background: The root-zone restriction cultivation technique is used to achieve superior fruit quality at the cost of limited vegetative and enhanced reproductive development of grapevines. Fungal interactions and diversity in grapevines are well established; however, our knowledge about fungal diversity under the root-zone restriction technique is still unexplored. To provide insights into the role of mycobiota in the regulation of growth and fruit quality of grapevine under root-zone restriction, DNA from rhizosphere and plant compartments, including white roots (new roots), leaves, flowers, and berries of root-zone restricted (treatment) and conventionally grown plants (control), was extracted at three growth stages (full bloom, veraison, and maturity). Results: Diversity analysis based on the ITS1 region was performed using QIIME2. We observed that the root-zone restriction technique primarily affected the fungal communities of the soil and plant compartments at different growth stages. Interestingly, Fusarium, Ilyonectria, Cladosporium and Aspergillus spp observed in the rhizosphere overlapped with the phyllosphere at all phenological stages, having distinctive abundance in grapevine habitats. Peak richness and diversity were observed in the rhizosphere at the full bloom stage of control plants, white roots at the veraison stage of treatment, leaves at the maturity stage of treatment, flowers at the full bloom stage and berries at the veraison stage of control plants. Except for white roots, the diversity of soil and plant compartments of treated plants tended to increase until maturity. At the maturity stage of the treated and control plants, the abundance of Aspergillus spp. was 25.99 and 29.48%, respectively. Moreover, the total soluble sugar content of berries was 19.03 ^obrix and 16 ^obrix in treated and control plants, respectively, at the maturity stage. Conclusions: This is the first elucidative study targeting the fungal diversity of conventional and root-restricted cultivation techniques in a single vineyard. Species richness and diversity are affected by stressful cultivation known as root zone restriction. There is an association between the abundance of Aspergillus spp. and fruit quality because despite causing stress to the grapevine, superior quality of fruit is retrieved in root-zone restricted plants.

Methoxypyrazines (MPs) are a unique class of volatile compounds containing nitrogenous heterocyclics that impart green bell, vegetal and herbal odors to red grape berries and wines. In this study, the quality and MPs levels of grape berries from six representative red wine grape varieties were determined in the two consecutive years. The results showed that, at maturity, the highest total soluble solid was observed in Petit Verdot grape berries in the two consecutive years. While the anthocyanin content showed the highest in Marselan berries in 2018, in 2019, Petit Verdot berries had the highest anthocyanin content. Moreover, 2-methoxypyrazine (MOMP), 3-methyl-2-methoxypyrazine (MEMP) and 3-ethyl-2-methoxypyrazine (ETMP) levels were relatively lower, with almost no detectable in berries at maturity. The relative higher 3-isobutyl-2-methoxypyrazine (IBMP) content was observed in Cabernet Sauvignon, Marselan, Merlot, and Malbec berries. However, 3-sec-butyl-2-methoxypyrazine (SBMP) and IBMP were only detected in six wines, and their levels were higher than those in the grape berries. Furthermore, correlation analysis showed that there was a statistically positive correlation between the expression levels of VvOMT1 and VvOMT3 and MPs content in grape berries, while the lowest association was found in the VvOMT2. These findings provide a basis for selecting the most suitable grape varieties to improve wine quality.

Root restriction cultivation (RRC) can influence plant root architecture, but its root phenotypic changes and molecular mechanisms are still unknown. In this study, phenotype observations of grapevine root under RRC and control cultivation (nRC) at 12 time points were conducted, and the root phenotype showed an increase of adventitious and lateral root numbers and root tip degeneration after RRC cultivation from 70 days after planting (DAP). The 70 and 125 DAP sampling of two different cultivations, named nR70, RR70, nR125, and RR125, were selected for small RNA sequencing. A total of 153 known miRNAs and 119 predicted novel miRNAs were obtained. Furthermore, BLAST was used to predict the novel miRNAs with miRBase databases using the default parameters; 96 of the 119 predicted novel miRNAs were similar to other species, and the remaining 23 grapevine-specific novel miRNAs were obtained. There were 26, 33, 26, and 32 miRNAs that were differentially expressed in different comparison groups (RR70 vs. nR70, RR125 vs. nR125, nR125 vs. nR70 and RR125 vs. RR70). Target genes prediction of differentially expressed miRNAs was annotated on a variety of biological processes, and 24 participated in root development. Moreover, multiple miRNAs were found to jointly regulate lateral root development under root restriction conditions. The miRNA expression pattern comparison between RRC and nRC may provide a framework for the future analysis of miRNAs associated with root development in grapevine.

Soil burial is a survival strategy for grapevines that can safely overwinter in north-western regions of China. A suitable training system was beneficial for soil burial to provide winter protection. Moreover, the training system can also significantly affect fruit quality during the development of grape berries, such as primary and secondary metabolites. In this study, four-year-old Cabernet Gernischt grapevines were used as experimental material and exposed to four training systems, including the Ningxia traditional vertical trunk (control, CK); the gobelet (T1); single guyot (T2); slant trunk with vertical shoot positioning (STVSP) (T3). The results showed that total soluble solid total phenol content was 12.69%, 57% higher under T3 training systems than in the control, and T3 alleviated the canopy density, leading to improving the leaf photosynthetic efficiency gas chromatography-mass spectrometry (GC-MS) assay used to detect the aroma compounds. The results indicated that the T3 training system enhanced the accumulation of alcohols, carbonyl compounds, C6/C9 and esters, which account for the largest proportion of volatile compounds, and the qRT-PCR reveals that VvEcar, Vvter, VvCCD1, and VvLis were raised under T3 at the transcriptional level. Moreover, T3 contributes to most free amino acid synthesis. Additionally, the PCA reveals the correlation of free amino acids under four training systems, which reflected the mostly amino acid related to T3, and thus, we could speculate that T3 enhances the overall aroma. These results may lead to new strategies to select a new, short trunk training system to achieve mechanized buried soil, to prevent cold and produce high-quality wine in this area.

Root restriction, as an efficient cultivation method, has been widely used to promote grapes fruit quality. In China, root restriction cultivation is usually implemented in the production of table grape berries to get higher yield planting in hot and humid environment. It is well known that endogenous plant hormones play an important role in plant growth and development, flowering and ripening, but the effect of root restriction on endogenous plant hormone contents in grape is still unclear. Therefore, it is very important to build a database of grape endogenous hormone contents with root restriction treatment. These data not only provide a reference for the analysis of fruit quality under root restriction, but also lay a theoretical foundation for the variation tendency of grape endogenous hormone contents. In this study, a total of 84 samples (3 biological replicates) were collected from different tissues and organs in different developmental stages of ‘Muscat Hamburg’ grape and analyzed by high performance liquid chromatography (HPLC). Thirteen endogenous plant hormones were identified and a comprehensive dataset of endogenous plant hormones in different organs and developmental stages of ‘Muscat Hamburg’ grape was established. The results provided data support for rapid detection and quantitative analysis of endogenous plant hormones in grape under root restriction cultivation.